This invention relates to a safety guard for power presses, such as press brakes, punch presses, shears, and the like.
A power press is conventionally equipped with a safety mechanism for protecting the operator as the ram or power member of the press descends toward the work material. Examples of such safety mechanisms are described in my prior U.S. Pat. Nos. 3,213,992; 3,269,215; and 3,464,291.
The invention relates to an improved safety mechanism which provides reliable, safe operation. The safety guard or shield reciprocates within a frame mounted on the power press, and the ram of the power press cannot be activated until the safety guard reaches its lowermost position. A lightweight sensory board is mounted on the safety guard for sensitive detection of any object in the path of the descending safety guard, and if the sensory board engages an object, such as the operator's fingers, the sensory board will be raised relative to the safety guard to close a switch and cause the safety guard to be raised to the up or safety position. The normally closed switch operated by the sensory board is mounted on the reciprocating safety guard, and an electrical connection between the switch and the frame is made through bus rods which are mounted on the safety guard and are slidably engaged with a contact member on the frame. The safety guard is operatively connected to a control member which couples the foot pedal or other operating member of the power press and the clutch for the ram. When the foot pedal is depressed, the control member activates a power cylinder for the safety guard to lower the safety guard and prevents the clutch from transmitting power to the ram until the safety guard reaches its lowermost position. When the safety guard reaches its lowermost position, it closes a switch to cause the control member to couple the foot pedal and the clutch, and the foot pedal can then be further depressed to lower the ram. If the press is equipped with a full revolution clutch, the safety guard remains down throughout the full cycle of the ram. If the press is equipped with a part revolution clutch, the safety guard returns to its up position when the ram cycle passes 180.degree. of its stroke and the ram rises. On the latter type of press, if the sensory board is raised to cause the held-open normally closed switch on the safety guard to close when the ram is descending, the control member uncouples the clutch, and the ram stops.